The transplantation of tissues or other organs from a healthy donor to a recipient who has suffered irreparable damage or disease, has its origins in ancient medical history. Organ and tissue allo-transplantation, though artificial, is the short-term solution and long-term cure for maintenance of functional and disease-related failure of select organ systems. Kidney, heart, liver, cornea, and bone-marrow transplants are commonplace; steady progress in skin, pancreas and lung transplantation is evident.
Conventional immunosuppression is used to prevent or ameliorate allograft rejection; it is an anti-proliferative and anti-differentiation chemotherapy designed to disarm the immune system.
Many immunosuppressive drugs in use today were initially applied as therapy for cancer; they are highly toxic to dividing cells. Blanket immunosuppression, however, is dangerous, especially for cells residing in bone marrow and the small intestine. Opportunistic infections by cytomegalovirus and herpesvirus, by various fungi, mycobacteria and by protozoans, are also a problem; increased risk of neoplasia is a suspected result of prolonged immunosuppression.
When tissue is transplanted from one location to another within or on the same individual, the prefix "auto-" is used. Thus, as used herein, the term "autologous" or "autogeneic" refers to those tissue graft situations wherein the donor and recipient are the same individual. The donor tissue is genetically identical to that of the recipient since they are one and the same. As used herein, the term "allograft" or "allogeneic" refer to those tissue graft situations wherein the donor and recipient are genetically different individuals within one species.
Bone marrow transplant has been the treatment of choice in a variety of diseases such as breast cancer, Hodkin's disease, non-Hodkin's lymphoma, and especially certain leukemias, and immunodeficiency disorders. There are several deleterious phenomena associated with bone marrow transplantation. Incidences of bone marrow graft rejection and/or leukemic relapse are quite common. Bone marrow transplantation is also notable because the recipient may be immunoincompetent, but the bone marrow graft often contains immunocompetent cells. This arrangement can lead to yet another phenomenon deleterious to successful tissue engraftment, and that is graft-versus-host reactions.
For example, allogeneic bone marrow transplantation (BMT) has demonstrated clinical efficacy for the treatment of refractory leukemia and genetic hematological disorders. However, a major barrier to successful allogeneic transplant has been this development of severe, and sometimes fatal, post-transplantation graft vs. host disease (GVHD). Recent advances in immunosuppressive therapies for GVHD prophylaxis have demonstrated tremendous success in reducing GVHD after HLA-identical transplants. However, for HLA-nonidentical transplants, in addition to conventional immunosuppressive regimens, it is generally recognized that some form of ex vivo T cell depletion is essential to keep GVHD under control. Methods employed for T cell depletion include, inter alia, the utilization of monoclonal antibodies against T cell surface antigens together with complement to trigger selective cytolysis, antibody-coated magnetic beads, elutriation and physical separation by soya bean agglutinin. These procedures, despite being very effective in T cell depletion, are usually time consuming, labor intensive and occasionally result in low cell recovery.
Further, while several clinical trials indicate that both the incidence and severity of GVHD in engrafted patients are reduced if bone marrow is depleted of donor T-lymphocytes, there has been an increased incidence of graft rejection and leukemic relapses in these patients. It has recently been shown that the use of antibodies against selected T cell subsets or partial instead of complete T cell depletion appear to yield better results, at least in terms of graft rejection.
Secondly, during autologous bone marrow transplantation (ABMT), patients' bone marrow samples, though harvested during remission, usually still contain a small percentage of leukemic cells which give rise to a high rate of post transplantation relapses. However, if the marrow is purged free of leukemic cells with selective o reagents that exert minimum impact on marrow progenitors that are required to reconstitute the hemopoietic system of the patient, the chance of relapses will be much lower.
The reagent that is currently used by many centers to purge the leukemic contamination in bone marrow preparations is an activated form of cyclophosphamide, 4HC (4-hydroperoxy-cyclophosphamide). This reagent is very effective in removing leukemic cells (average D.sub.10 for leukemic cells is about 30 ug, wherein D.sub.10 is defined as 1 log of depletion) but is also quite toxic to marrow cells (D.sub.10 is about 50 ug) and the therapeutic window is relatively small (therapeutic index.apprxeq.1.67).
Polyamines such as sperminc, spermidine and putrescine are widely distributed in mammalian cells, although they are found to differ in their relative concentrations. The literature is replete with reports of these compounds or certain of their metabolites, possibly being involved in biological activity such as immunosuppression activity and other inhibiting activity. For example, oxidized polyamines are believed to inhibit growth of parasites (D. M. L. Morgan and J. R. Christensen, Adv. Polyamine Res., 4, 169-174 (1983); D. M. L. Morgan, U. Bachrach, Y. G. Assaraf, E. Harari and J. Golenser, Blochem. J., 236, 97-101 (1986)), suppress infectivity of selected strains of phage and bacteria (U. Bachrach, S. Don and H. Wiener, J. Gen. Virol., 13(Pt. 3), 415-22 (1971); K. Nishimura, T. Komano and H. Yamada, Blochim. Biophys. Acta, 247(1), 153-6 (1971) J. G. Hirsch and R. J. Dubos, J. Exp. Med., 95, 919 (1952); C. W. Tabor and S. M. Rosenthal, J. Pharmacol., 116, 139 (1956)) and inactivate several strains of viruses (U. Bachrach and E. Rosenkovitch, Appl. Microbiol., 23(2), 232-5 (1972); U. Bachrach and S. Don, J. Gen. Virol., 11(Pt. 1), 1-9 (1971); U. Bachrach, C. W. Tabor and H. Tabor, Biochem. Biophys. Acta, 78, 768 (1963); U. Bachrach and J. Leibovici, Isr. J. Med. Sci., 1,541 (1965); J. Schindler, Experientia, 21,697 (1965); E. Katz, T. Goldblum, U. Bachrach and N. Goldblum, Isr. J. Med. Sci., 3,575 (1967)). The literature does not make clear however, whether the inhibitory effect is due to aminoaldehydes or other toxic side products such as hydrogen peroxide and ammonia released during the oxidation of spermine by PAO.
Hence, despite the impressive list of studies performed with oxidized spermine, the actual molecular structure(s) mediating the specific immunosuppressive or inhibitory activities is unknown. Oxidation of spermine by PAO revealed six major oxidation products in addition to ammonia and hydrogen peroxide (R. S. Labib and T. B. Tomasi, Jr., Eur. J. Immunol., 11,266-269 (1981)). The inhibitory effect of each of the products has not been analyzed but it was believed that the dioxidized sperminc or sperrnine dialdehyde (NN'-Bis-(3-propionaldehyde) -1-4-diaminobutane) would demonstrate activity. Israel et al, (Supra) (1973), synthesized this molecule together with another analogue and found that both compounds exhibited cell inhibitory activities in vitro. These investigations however failed to find significant in vivo efficacy with the dialdehydes they synthesized. Furthermore, these molecules were quite toxic, sperminc dialdehyde (NN'-Bis-(3-propionaldehyde)-1-4-diaminobutane) showed severe acute toxicity with an LD.sub.100 at 40 mg/kg when given intraperitoneally.